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' J. WICKS MULTIOFFICE TELEPHONE SYSTEM Filed Nov. 15 1919 9Sheets-Sheet 1 Jul-1n ibks I I Sept. 30., 1924. 1,510,1 4

J. IWICKS MULTIOFFICE TELEPHONE SYSTEM Filed Nov. 15. 1919 9Sheets-Sheet 2 'lnuenim" JuhnYn/Eks Fifi 7 p Sept. 30. 1924. 1,510,124J. WICKS MULTIOFFICE TELEPHONE SYSTEM Filed Nov. 15 1919 9 Sheets-$heety [W Jul-m MHz ks Sept. 30, 1924. 1,510,124

J. WICYKS MULTIOFFICE TELEPHONE SYSTEM Filed Nov. 15, 1919 9Sheets-Sheet 4 [nusniur Juhn MERE Sept. .30, 1924. 1,510,124

J. WICKS MULTI OFFI CE TELEPHONE SYSTEM Filed Nov. 15 1919 9Sheets-Sheet 5 [limb-r Jul-m 11/1515.

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Spt. 30,1924. 1 1,510,124

J. wlcKs MULTIOFFICE TELEPHONE SYSTEM Filed Nov. 15 1919 9 Sheets-Sheet6 I'm" Juhn Zn/Taks HIT y:

Sept. 30. 1924. 1,510,124

' J. wlcKs A MuLT16FFIcE TELEPHONE SYSTEM Fil ed Nov. 15, 1919 9Sheets-Shet 7 [nuanlnr Jmhn Znlzcks Sept. 30, 1924. 1,510,124

J. WICKS MULTIOFFICE TELEPHONE SYSTEM Filed Nov. 15. 1919 9 Sheets-Sheet8 1m Jul-m HzEks Sept. 30, 1924. 1,510,124

J. WICKS MULTIOFF'ICE TELEPHONE SYSTEM Filed Nov. 15. 1919 9Sheets-Sheet 9.

'6 7 a ,Start' 11111511151 J 'h W1 i;

Patented Sept. 30, 1924.

1,510,124 PATENT OFFICE.

JOHN WICKS, OF CHICAGO, ILLINO'IS, ASSIGNOR T0 AUTOMATIC ELECTRIC.COMPANY,

' OF CHICAGO, ILLINOIS, A CORPORATION OF ILLINOIS.

MULTIOFEIOE TELEIHONE 'SYSTEML Application filed November 15, 1919.Serial No. 338,380.

ephone Systems, of which the following is a specification. ,i Myinvention relates in general to multioffice telephone'systems andisparticularly well adapted for use in such systems as are going thru aperiod of transition from man ual'operation to automatic operation,there being-some offices or exchanges of the system which have fullautomatic equipment while the other oflices still have the manualequipment. However, certain features of the invention are of value inordinary manual inulti-oifice systems not including automatic equipment,while certain other features are applicable to the so calledsemiautomatic I systems, although it is conceived that the-inventionbroadlywill find its chief use under the circumstances firststated.

In changing a large manualmulti-ofiice system 'over'to automaticequipment it is considered thebest practice to do so gradually, oneoffice at a time, rather than to attempt to change all ofiices at once.In fact the latter method would in practice be very diliicult if notimpossible to accomplish successfully. It follows therefore that afterthe changeover is started and until it is completed certain of theoffices will have auto matic equipment while the others still have theoperators, The 'problem then is pre sented of providing suitabletrunking facilities between manual and automatic exchanges. I v Thisinvention is not concerned especially withthe trunking from theautomatic exchanges to the manual, there being suitable means availablealready for handling such traffic, but itsobject is toprovide a newv andbetter arrangement of trunking from the manual oflices'to theautomaticofiices, and incidentally,'in order topermit a uniform routine ofoperation on the part ofthe operators, to provide an improved trunkingarrangement between the manual oflices themselves. J I, I

o Other objects jconsist in providing improved circuit details andmechanism which with the improved trunking arrangements above mentionedwill be fullydescribed heretermed the No. 1 oflice or exchange.

inafter, reference being had to the accom panying drawings.

Referring to the drawings, Fig. 1 is -a schematic diagram showing thetrunking arrangement between two manual offices, while Figsy3 and 4 arecircuit diagrams showing the apparatus required to establish a completeconnection between subscribers in ,dif ferent manual oflices which areinterconnected by a system of trunks such as is shown in Fig. l. Theleft hand portion of Fig. 1 up to the dotted line and Fig, 2 shows aschematic diagram of. the trunking arrangement used for handling callsfrom a manual oflice to an automatic ofiice. The remaining sheets ofdrawings, Figs. 5 to, 9,.-inelusive, taken inv connection with Fig. 3,show circuits of the apparatus used in completing a connection from asubscriber in the manual oiiice to a subscriber in an automatic oflice,according to the second trunking arrangement, or at least so much of thecircuits is shown as is necessary to enable the invention to beunderstood. .The general system of trunking from a manual oflice to asecond manual officewill first be briefly explained. Referring to Fig.1, jacks J to J are four of a plurality of outgoing trunk jacks at the Aboard of a manual ofiice which will hereinafter be These jacks arepreferably multipled in a certain number of other positionsas'indicated; and are directly connected to primary rotary line switchesP tol, respectively. Thesel-ine switches may be of 25 line capacity andas each of the switches shown has access toa different plurality oftrunks there will be 100 trunks extending to the second or No. 2manual'oiiice. Each of these trunks terminatesat the No. 2 office in asecondary rotary'line switch, and four of these switches are indicatedby reference characters S to The number of cord circuits at the B- boardin the No. 2 exchange for handling calls from the No. 1 exchange shouldbe somewhat in excess of thenumber of trunks, allowing for repairs, etc,and we may assume that 120 cord circuits are provided which are dividedinto two groupsof cord circuits for each of two positions. Four cordcircuits C to C are shown,-which arelocated at thelst position and theother four, C to C are at the 2nd position. These cord circuits areaccessible tothe sec ondary switches such as S, S etc., and maybemultiplied in the banks of these switches as desired, care being takenhowever to give each switch access to cord circuits in both positions.In the present case the switches S, S etc., may be 30 point switches andmay be divided into 4 groups having access to 15 cord circuits at eachposition. Of course the capacity of the switches is immaterial, and theymay be of any desired capacity. It has been stated above that the jacksJ, J etc., are multipled in other positions. In the case of a large Aboard as is herein contemplated it will usually be best to divide theboard into two or more sections and multiple the first group of outgoingtrunk jacks only in the first section which may arbitrarily have 10 ormore positions, the term section as here used not referring to thestandard 3 position section. An independent multiple will be providedfor each of the other sections, one such being represented by the jacksJ, J, etc., which are connected to primary switches P, P, etc. Theseswitches have access to the same groups of trunks as do the switches P,P etc. Thus it will be seen that an excessively large outgoing trunkmultiple at the A board will never be required.

It will be understood that the foregoing explanation considers only thetrunking between the No. 1 ofiice and the No. 2 oflice. There will be asimilar system of trunks extending from the No. 1 office to each of theother manual offices, as is the usual practice. Likewise there will be asystem of trunks from the No. 1 ofiice to each of the automatic ofiicesin the system and the trunking to one of these offices, which will betermed the No. 3 oflice, will now be explained.

The outgoing trunk multiples at the A board of the No. 1 oftice areidentical so far as general arrangement and trunking is con cerned,whether they extend to manual oflices or to automatic oflices. In viewof this fact, it is not considered necessary to show the outgoing trunkmultiple to the N0. 3 office because for purposes of illustration Fig. 2may be joined to Fig. 1 at the dotted line so that the four trunk lineswhich extend from the first contacts of primary switches P to P willcontinue into Fig. 2 and terminate in secondary switches S to Srespectively. These latter switches may be of 30 trunk capacity and aredivided into four groups, there being shown one switch of each group.There will be therefore a total. of 120 trunks in the layout as shown,and each trunk extends by way of a relay equipment such as M to a firstselector switch such as H. It will be seen that there are two Boperators positions, each being arranged to handle 60 trunks.Considering the first position, the 60 trunks are divided intothreegroups of 20 trunks each and calling devices or operator's sendersN, N, and. N are provided which control the establishment of connectionsover the 3 groups of trunks, respectively. All three senders are in turncontrolled by the operator thru the medium of a set of keys indicated byreferences character K. The arrangement at the second position is thesame. In multiplying the trunks in the banks of the switches S S, etc.,the arrangement should be such that there are a certain number oftrunks, 5 in this case, extending from the banks of each of the fourgroups of switches to each of the 6 operatorssenders; or in other words,the 20 trunks controlled by each sender should be divided into as manygroups as there are groups of secondary switches and each group oftrunks should then be multipled in the banks of a different group ofswitches.

The foregoing will be sufficient it is believed to make clear thegeneral layout of the system. The method of operation and the circuitswill be described fully in the de tailed specification which is tofollow. In order to reduce the amount of descriptive matter in thespecification, the apparatus used, such as the automatic substations,the primary and secondary line switches, the selector switches and otherswitches comprising the automatic exchange, and the operators sendersand key equipment, will not be described in detail, but insteadreference is made to the following patents: British patent to Dicker#29554 of 1910, U. S.

patent to Land #1,14t6,177, U. S. patent to Lamb $51,193,160, U. S.patent to Keith Erickson and Erickson #815,321, U. S. patent to KeithErickson and Erickson #815,- 176, U. S. patent to Blessing 51,209,253,'U. S. patent to Powell #1,308,553.

Having given a general description of the trunking system as a whole, Iwill now describe the operation thereof more in detail, it being assumedfirst, referring to Figs. 3 and et, that the subscriber at substation Awhose line is connected to the No. 1 office desires to obtain connectionwith the subscriber at substation A whose line is connected to the No. 2ofiice. Vhen the subscriber at substation A removes his receiver fromthe hook a circuit is completed which extends from ground thru the cutoff relay 2, over the line and thru substation A, and returning on theother side of the line thru the line relay 3 to battery. The line relay3 is energized upon the closure of the above circuit and completes acircuit for the line lamp L; but relay 3 being of high resist ance, thecut off relay 2 is prevented from energizing at this time. \Vhen theoperator observes the lighted condition of the lamp L she will respondby inserting the answering plug of an idle cord circuit, for example thecord circuit C, in the jack J, at the same time throwing her listeningkey K. Upon the insertion of the plugin. the jack a circuit is completedover the tip of the plug which connects the cut off relay 2 and therelay 4.01 the cord circuit in series. Both relays are energized, relay4 closing a pair of contacts in the circuit of the supervisory lamp L,and the cut cit relay switching the ring side of the line fromconnection with the line relay 3 into connection withthe sleeve of jackJ, thereby placing a potential upon the sleev'eoif jack J and itsmultiples (not shown) whereby the line of substation A is made busy atother positions. At the same time that relay 4 is energized as describedrelay 5 is also energized over a circuit which extends from ground thruout off relay 2, thrusubstat ion A, and back over the ring side of theline thru relay ,5 to battery. Relay 5 opens a pair of contacts in thecircuit of the supervisory lamp L.

,Vhen the subscriber at substation A hears the operator on the line, hewill re peat the number of the subscriber with avhoni he wishes to beco-i'inected, as is the well known practice. Upon learning that thedesired subscriber IS in the No. 2 ofiice,

" the operator will test the outgoing trunk locate an idle jack.

multipleot the No. 2 office with the tip of her plug in the usual mannerin order to Assuming that the jack J is found to be idle the operatorwill insert the calling plug, whereupon. a circuit is completed for therelay 6 as follows:

" Ground at G, restingcontact of armature 18 andthe said armature, ringspringof jack J", ring of plug, and the winding of relay 6 to: battery.Upon energizing, relay 6 opens a pair of contactsin the circuit of thelamp L and also completes an initial energizing circuit for relay 7which extends as follows; Ground at G windingof relay 11 tip spring ofjack J, tip of plug, contacts of relay .6, and the winding of relay 7 tobattery. Upon energizing relay 7 closes its own circuit independent ofrelay,

6 and also prepares a circuit for the'supervisory lamp L w Theenergization. of relay 1.1, which is the line relay of the primary lineswitch P", over the circuit described above, causes the initiation ofthe trunk selecting movement of this switch whereby an idle trunk lineextended to the No. 2'o1fice is selected.

Upon attracting its armature 14, relay 11 I test contact with which thetest wiper 22 is 21, 22, and 23 step by step in search of an idle trunkextending to the No. 2exchange.

This is the usual operation of a rotary switch otthis type in the casewhere its operation is initiated when its wipers are standing upon thecontacts of a trunk line which is busy. However, in the present case wemay assume that when the operation of the line switch P is initiateditswipers are standing upon the contacts which are terminals of thetrunk conductors and 27 as shown in the drawing, and we may assumefurthermorethat this trunk line is idle at the time. Under thesecircumstances, when the circuit of the switchingrelay 12 is closed thruthe stepping magnet 13 the said relay 12 will not be short circuited andthe stepping magnet will not operate owing to the high resistance ofrelay 12; The relay 12 is energized with the following re sults; At itsarmature 18 ground G is disconnected from the ring side of the linecircuit thereby causing relay 6 in the cord circuit to deenergize andclose the circuit.

of the calling supervisory lamp L 1 At armature 17 ground G? isconnected to the test wiper 22 thereby completing a circuit over theconductor 26 to the'relay 28,'which is one of a series of chainrelays'which are provided, one for each trunk, for the purpose ofconnecting battery to the common conductor 29 whenever all the outgoingtrunks in the group become busy, The

sleeves of the jack are all normally con- 'nected to this commonconductor 29 by way 'tacts of armatures 33 and 34-. of relay to thewinding of the line relay 31 of the secondary line switch S.

It will be seen that the line relay 31 is thereby bridged across theline and will be energized by current flow from ground at G thru theline relay 11 of the primary line switch 1P, over the upper lineconductor, thru the said line relay 31, over the lower line conductorand thru the winding of relay"6 of the cord circuit C to battery.

Relay 31 is of high resistance and does not permit enoljlgh current toflow to cause the operation of relay 6, but energizes immediately itselfand closes a circuit for the relay 32. Upon the operation of relay 32circuits are closed which correspond to similar circuits whose operationhas been described in connection with the primary line switch P,

whereby the secondary switch S is caused to select and establishconnection with an idle cord circuit. These operations having alreadybeen described will not be considered again in detail, but it will besuf iicient to say, assuming that the cord circuit C is idle, that theswitching relay 30 is energized, whereby the line conductors areextended by way of armatures 33 and 34 and their working contacts,wipers 4L0 and 42, the bank contacts with which these wipers are inengagement, and the upper and lower windings of the repeating coil R tothe windings of the relay 60. Relay 60, or at least its left handwinding, is of high resistance and this relay is now energized over a.circuit similar to that by which the line relay 31 of the secondaryswitch S was energized, relay 6 at the cord circuit C" re maininginoperative as before. Upon energizing, relay 6O completes a circuitwhich extends as follows: Ground G working con tact of armature 82 andthe said armature, and the winding of relay 43 to battery. Uponenergizing in its turn, relay 43 completes a holding circuit for theswitching relay 30 of secondary switch S which may be traced over thefollowing path: Ground at G working contact of armature 49 and the saidarmature, resting contact of armature 83 and the said armature, testcontact upon which the test wiper ll is now resting and the said testwiper, armature 35 and its working cont-act, winding of the switchingrelay 30 and the winding of the stepping magnet 36 to battery.

It is understood that this holding circuit is established before theslow acting relay 32 has had time to deenergize. A branch of the holdingcircuit just traced extends by way of the resting contact of armature 52and the said armature to the common conductor 59, thereby grounding thisconductor. Conductor 59 is multipled to contact springs corresponding toarmature 52 in all the other cord circuits at the position, and whengrounded therefore has the function of rendering all the cord circuitsbusy.

As a further result of the energization of relay 43 ground G isconnected by means of armature 50 to the windings of relays l5 and 64-,both of which relays are energized. Relay d5 at its arn'iatures 57 and58 connects the operators head set across the trunk circuit whereby sheis put in communication with the operator at the No. 1 exchange. Relay64 at its armature 7O closes a circuit for the lamp L" which extends asfollows: Ground at. G interrupter I, normally closed contacts controlledby armature 73 of relay 63, armature 74- and its resting contact,working contact of armature and the said armature, and thelamp L tobattery.

Connection having been established between the two operators, the Aoperator will now repeat the desired number to the B operator who, beingadvised which of her cord circuits is to be used by the flashing of thelamp L will test the desired line and upon finding it idle will insertthe plug of cord circuit C in multiple jack J Upon the insertion of theplug a. circuit is completed for the relay 62 as follows: Ground at Gwinding of relay 62, resting contact of armature 7 8 and the saidarmature, resting contact of armature 79 and the said armature, ring ofplum ring spring of jack J normally closed contacts of the cut off relay2, and the winding of the line relay 3 to battery. Upon energizing,relay -62 closes the following circuit: Ground at G, working contact ofaimature 75 and the said arm-a.- ture, winding of relay 67, and theresistance r to battery. Relay 67 is energized and at its armature 76completes an energizing circuit for relay 66 which relay at its armature78 opens the circuit of relay 62. Upon deenergizing, relay 62 breaks theoriginal energizing circuit of relay 67, but this relay is notdeenergized, remaining locked up over the following path: Ground at G,winding of the cut off relay, tip spring of jack J tip of plug, armature80 and its working contact, the winding of relay 67, and the resistancer to battery. ,As a further result of the energization of relay 66 theupper and lower line conductors are closed at the working contacts ofarmatures 77 and 78, and at armature 7-1 the circuit of the lamp L isbroken. ln addition, at the working contact of armature 74 a circuit isestablished for relay 63 as follows: Ground at G interrupter I (thefirst time this interrupter closes the circuit), normally closedcontacts controlled by armature 73 of relay 63, armature 74 and itsworking contact, armature 69 and its working contact, and the winding ofrelay 63 to battery. Upon energizing, relay 63 locks itself independentof relay 64 at its armature 72, and by means of armiature 73 substitutesdirect ground for the interrupted ground G A branch of the circuit bywhich relay 63 was energized may be traced from the junction point 84 byway of armature 56 and its working contact, normally closed contactscontrolled by armature 5i, and the winding of relay 44 to battery. Uponenergizing relay 4% completes a locking circuit for itself at itsarmature 51; breaks the circuit of relay 45 at its armature 53, wherebythe operators head set is disconnected from the trunk; and at armature52 removes ground G from the com- I projected out over the called linein the usual 1 Responsive to the hanging up of the re manner to signalthe called subscriber. Relay '68 is included in this circuit and is soadjusted that it does not respond to the ringing current as long as thereceiver at the called station is on the hook. hen the called subscriberanswers, however, relay 68 isoperated, either byringing current from thegenerator Gen or by direct current from the battery associatedtherewith, and shortcircuits the winding of the ringing relay 67. Relay67 is accordingly deenergized and in addition to breaking itsownloc-king circuit at armature this relay opens the originalenergizingcircuit of relay 66, which is hereafter maintained energizedover the tip side of the line to ground G thru the winding of the cutoff relay 2, As a further result of its deenergization, relay67disconnects the ringing current generator and closes the ring side ofthe line at armature 79. The

rec-eiverbeing off the hook atthe called station a circuitis nowestablished which extends fromground G thru the winding of erated toextinguish the supervisory lamp L The A operator, who has alreadyrestoredher keyK, is thus notified that the call has been answered andneed pay no further attention to it until one or both of the lamps L andL are again lighted to in-f dicate that the conversation is finished.

The talking circuit between the two connected sub-stations is shown inheavy lines,

and being furthermore of well known character, willnotnee'dto bedescribed in .de-

tail. lVhen the conversation' is over with both subscribers willreplacetheir receivers.

ceiver at substation A the circuit ofrelay 5 is broken, resulting in thelighting of the supervisory lamp L. l V'hen the receiver is replaced atsubstationiA relay 61 is deenergized and the high resistance winding ofrelay 60 is again included in the circuit of relay 6 at the cord circuitC, thereby causing this relay to de'energize and close the circuit ofsupervisory lamp L The lighting of the supervisory lamps indicates tothe operator that the subscribers are tru talking and she willacordingly pull down the connection. \Vhen the calling plug is removedfrom jack J the circuit of relay 11 of the primary line switch P isbroken, whereupon this relay and also the switching relay 12 aredccnergized, thereby restoring the'switch to normal condition ready foranother call. As a further result of the removal of the plug from jack Jthe circuit of relay 60 of cord circuit C is broken and this relaytherefore deenergizes to break the circuit of relay 4?). Upondeenergizing, relay 13 breaks the holding circuit of theswitching relay30 of the secondary line switch S at its armature 19, whereupon relay 3Odeenergizes and the secondary line switch is restored to normal 1 itsworking contact, armature 56 and its rest-V ing contact, armature 4C7and its resting contaot, and the winding of relay -16 to battery. Relay4:6 is operated and again grounds the test contact upon which test wiper41 is resting, and multiples of this test contact (not shown), wherebythe cord circuit C is again made busy to incoming calls, the briefinterval during .which ground is removed- I from the test contact beingjust sufiicient to provide for the restoration of the secondary switchS. As a further result of the deenergization of relay 13, ground G isdisconnected from the relay 6& and this relay therefore deenergizes toclose a circuit for the lamp L which extends as follows: Ground at G,armature 73 and its working contact, armature 74c and its workingcontact, resting contact of armature 'TOxand the said armature, and thelamp L tobattery. The lighting of the lamp L gives the B operator adisconnect signal, upon perceiving which she will remove the plug fromjack J As a result of the removal of'the plug, relay '66 is deenergized,breaking at its armature 74 the circuit of the lamp L and also thecircuit or relay46. Relay 46 therefore deenergizes also removing groundfrom the multiple test contacts associated with cord circuit C,whereupon the cord circuit Wlll be agaln n normal condition and readyfor another call.

Having described the operation of the circuits involved in theestablishment'of a connection between a subscribers-line connected tothe No. 1 oflice and a second subscribers line connected. to the No. 2ofiice, both of which ofiices have manual equipment, I will now describethe operation of the circuits involved in establishing a connectionbetween a subscribers line con-- nected to the No. 1 oiiice' and asubscribers .the desired line is connected to the numher .3 or automaticoffice. In this case, then, the A operator in order to extend theconnection will test the out going trunk multiple associated with theNo. 3 office, and upon finding an idle jack, assumed in this case to bejack J will insert the calling plug of the cord circuit C. When theoperator plugs into the jack the primary switch P will be operated toextend the connection to an idle trunk line which will be assumed to bethe trunk line extending to the secondary switch S Fig. 5; andimmediately thereafter the secondary switch S will operate to furtherextend the con nection to an idle relay equipment. Assuming that therelay equipment M, Fig. 5, is found to be idle and that connection isestablished therewith, the relay 128 will be energized over the linecircuit. Relay 128 will be recognized as a relay normally having a highresistance, corresponding to the relay 60 of cord circuit C. It followsthat relay 6 of cord circuit C will remain inoperative and thesupervisiory lamp L -will continue to glow. Upon energizing, relay 128closes the circuit of slow acting relay 129 which relay, upon attractingits armature 1 12, connects the righthand windings of the repeating coil*1 across the trunk conductors 161 and 162 The trunk line comprisingconductors 161 and 163 extends to a first selector switch (not shown)and it follows that upon the closure of the line circuit by theoperation of relay 129 the line and release relays of the first selectorwill be energized in the usual manner thereby preparing the selector foroperation responsive to interruptions subsequently produced'in the linecircuit in accordance with a digit in the called numher. At its armature1521 relay 129 also closes a contact in the circuit of relay 111 for apurpose to be described hereinafter; and at its armature 140 connectsground G to conductor 162. As a result of this latter operation thevisual signal V is actuated and also an energizing circuit is completedfor the slow acting. relay 130.

Relay 130 upon energizing completes a holding circuit for the secondaryswitch S as follows: Ground at G, working contact of 145 and the saidarmature, test contact with which test wiper 121 is in engagement andthe said test wiper, armature 109 and its working contact, winding ofrelay 106, and the winding of the stepping magnet to battery. Thiscircuit is established before the slow acting relay 108 has had time todeenergize, and in addition to its function of maintaining relay 106 inoperated position, it also provides ground to multiple test contactsassociated with the relay equipment M in the banks of other secondaryswitches for the purpose of rendering the relay equipment M busy toother calls. It will be observed that ground G also extends by way ofthe working contact of 1 5 and the said'armature, armature 148 and itsresting contact, and conductor 171 to conductor 171, Fig. 7. Conductor171 is a common conductor and has connected to it all the conductorssimilar to conductor 171 which are associated with the other relayequipments of the group which is controlled by the operators sender N.It will be seen therefore that as soon as the relay equip ment M isseized the common conductor 171 will be grounded, resulting in thegrounding of all conductors such as conductor 171 which extend to otheridle relay equipments in the group; and that since in all idle relayequipments the relays such as relay 130 are deenergized, the effect ofgrounding conductors such as conductor 171 will be to'placc a busypotential upon the test contacts associated with all the other idlerelay equipments of the group. But this is not all. There is a commonconductor such as the common conductor 171 sociated with each operatorssender, the common conductor associated with the second operators senderbeing indicated by reference character 271, Fig. 8. All three of thesecommon conductors, assuming that. the operator at this position hasthrcecallingdevices, or senders, are connection by way of normallyclosed relay contacts to another common conductor 201, there being onesuch latter conductor to each operators position. It follows thereforethat when the relay equipment M is seized, not only will all the otherrelay equipments of the group be made busy, but all the idle relayequipment of the groups associated with the other two operators sendersN and bl will be made busy also.

Returning now to the relay 130, as a further result of its energizationa circuit is completed for relay 132 which extends as follows: Ground atG, armature 2141 and its resting contact, normally closed contactsprings controlled by armature 225, conductor 16 1, armature 1&4 and itsworking contact, armature 1 17 and its resting contact, and the windingof relay 132 to battery. Upon energizing relay 132 connects theoperators head set across the trunk circuit by means of its armatures150 and 152; and at armature 151 closes a circuit for relay 202, Fig. 7,which may be readily traced over conductor 169. Relay 202 accordinglyenergizes and at its armature 228 disconnects ground from conductor 2 11for a purpose which will be explained later, and also at its armature226 connects ground .to

then depresses the key marked of relay 111 and associated circuits willbe explained later on. A, branchof the circult of relay 202 may betraced from junc tion point 242, Fig. 7, thru the windings of relays 243and 2 44 in series to battery. These two relays are therefore energizedand connect the conductors coming from the operators number setting orregister keys shown in Fig, 9 to the operators sender N. When. relay 132was energized it closed,-in addition to the circuits just described, acircuit which extends from ground G by way of'armature153 and itsworking contact and the windings of relays 133 and 134 in series tobattery. Upon energizing relay 133 establishes a locking circuit foritself and relay 134 which. may be traced as follows: Ground at G, Fig.7, normally closed contacts controlled by armature 217, armature 211 andits resting contact, normally closed contacts controlled by armature224, common conductor165 conductor 165,-ar1;pature 154 and its workingcontact, and the windings of relays 133 and 134 in, series to battery.At its armature 157 relay 133 connects ground to conductor 171 in orderto maintain this conductor grounded after the energization of relay 131which occurs at a further-stage of the operation; and at its armatures155 and 156 prepares circuits which need not be considered now as theyremain open for the time being at other points. Relay 134, uponenergizing, disconnects the trunk conductors 161 and 163 from the righthand windings of the repeatingcoil R and connects them instead toconductors 166 and 167, respectively, which are connected to commonconductors 166 and 167, respectively,'which terminate in the normallyclosed interrupter or impulse transmitting springs 245 and 246 of theoperators sender N;

The foregoing operations have all occurred automatically responsive tothe seizure of the relay equipment M by the secondary switch S 2 The Boperator having control of the sender 1 .will now be in communicationwith the A. operator, her

head sethavingbeen connected by the en-' er'gization of relay 132, aspreviously stated. The A operator knows when the connection to the Boperator has been completed by the cessation of the induced tone on theline (produced by signalling equipment Q whilerelay 107 is energized)and will now repeat the desired number. Upon learning the number the Boperator de presses in rapid succession the corresponding digit keys ofher .key set, Fig. 9, and start. The B operator ordinarily pays nofurther attention to the call after performing these operations.

In response to the actuation of the digit keys certain ones of aplurality of levers (not shown) arranged radially, on the wheel 249; areset by means of an arm (also not shown) operated by the magnet 252 andcontrolled by the solenoids 251. In. this way the required number isregistered on the wheel 249. Then the first digit key is depressed (andeach time a key is depressed thereafter during the setting up of thenumber) a circuit is closedas follows: Ground at G, winding of relay206, conductor 254, conductor 255, contacts of any depressed key,conductor individual to the depressed key, and the correspondingsolenoid of the sender N. to battery. This will make it clear how. thesolenoids and magnet 252 are energized at proper times, the lattermagnet being controlled by the relay206 which is energized in serieswith one of the solenoids every time a digit key is depressed. Relay206, at its first energization, closes a circuit for relay 207, whichupon. energizing, closes a locking circuit for itself at its'armature218. A circuit may now be traced from ground G by way of normally closedcontacts controlled by armature215,

working contact of armature 218 and the said armature, conductor 2'56,andlamp L to battery. Lamp L is lighted when the first keyis depressedand indicates that the sender-is in set or partially set position but isnot operating to transmit impulses.

Upon the operation of the starting key a circuit is closed for the relay209 as follows: b'rround at G, normally closed contacts controlled byarmature 215, working contact of armature 218 and the saidarmature,conductor 257, conductor 258, contacts of starting key, conductor 259,condu'ctor260, and

' the winding of relay 209 to battery. Upon attracting its armature 214,relay 209' opens the circuit of relay 132 which relay deenergizes withimportant results. By retraction of armatures150 and 152 the B operatorshead set is disconnected. By the retraction of armature 151 the circuitof relays 202, 243, and 244 is broken, and these relays are deenergized,the latter two disconnecting the register keys from the sender N, and bythe retraction of armature 153 a circuit for re lay 203 is closed asfollowsz'Ground at G, armature 153 and its resting contact, workingcontact of armature 155 and said armature, conductor 170, commonconductor 170, and the winding of relay 203 to battery. Upon energizing,relay 203 connects ground at its armature 227 to conductor 168 which itmaintains grounded after relay 202 has deenergized, and at its armature229 disconnects the common conductor 171 from the common conductor 201.By the latter operation the relay equipments of the groups controlledbycalling devices N and N are placed in idlecondition and are ready toreceive calls. This is proper, for although the sender N has not yetperformed its function (note that the relay equipments associated with Nare held busy for the present) still the operator has done her part, herhead set and register keys have been disconnected, and she may well busyherself by setting up another call on one of her other senders. As afinal result of its deenergization, relay 132 closes the circuit ofrelay 131, ground G being extended by way of armature 153 and itsresting contact, working contact of armature 156 and the said armature,and the winding of relay 131 to battery. Upon energizing, relay 1231establishes a locking circuit for itself at armature 1 18 and atarmature 147 opens a contact in the circuit of relay 132 to prevent thisrelay from energizing again after the sender N is restored to normal.

Returning to relay 209, an additional function of its energization isthe completion at armature 212 of a circuit for the starting relay 240of the sender N. Upon energizing the starting relay 24:0 closes thecontact springs 272 and 273 which are locked mechanically in closedposition. A circuit is thereby completed for relay 208 which uponenergizing, closes a locking circuit for relay 209 at its armature 215;breaks the circuit of relay 207 and of lamp L at the contacts controlledby the same armature; opens the circuit of starting relay 240 atarmature 216; and finally by attracting armature 217, inserts thewinding of the slow acting relay 210 in the previously described lockingcircuit of relays 133 and 13a of the relay equipment M. Relay 210 isaccordingly energized. A branch of the circuit of relay 208 extends overconductor 27 1 to lamp L which is now lighted. A further result of theclosure of springs 272 and 273 is the completion of the operatingcircuit of the motor 250 which now begins to rotate the wheel 249 andthe impulse cam 275, the gearing for driving the latter not being shown.The gears are so proportioned that the cam 275 separates the impulsesprings 245 and 246 once for each lever (not shown) on the wheel 249which passes the springs 276 and 277. As soon as the first displacedlever arrives at the latter springs they are closed momentarily therebycompleting a circuit for slow acting relay 247. Relay 2 17 closes inturn a circuit for slow acting magnet 248 which operates to bring a pawlinto engagement with the impulse cam, thereby stopping the operation ofthe motor for an interval. As soon as relay 247 and magnet 2 18 retracttheir armatures the motor again starts to revolve and another series ofimpulses is transmitted by the cam 275, the number of impulses beingdetermined as before by the displaced lever on the wheel 2&9. It will beclear, therefore, that the impulse sender N will operate to transmit inthis manner as many series of impulses over the circuit including trunkconductors 161 and 163 as there were digit keys depressed, the number ofimpulses in each series being determined by the relative position of thedisplaced levers, which in turn depends upon which digit keys weredepressed.

lVhile the automatic switches which re spoud to the several series ofimpulses to establish the connection are not shown, they have beendescribed in the patents referred to, and anyway they are wellunderstood by those familiar with the art. It will suffice to say inthis connection that a plurality of serially related selector switchesand a connector switch are successively operated by the successiveseries of impulses until the final switch which is the connectorcoinpletes the connection to the desired line, whereupon suitableringing mechanism is rendered operative to signal the calledsubscribe-r.

After the transmission of the last series of impulses, the motor 250continues to run until the wheel 21-9 has made a complete rotation andreturned to its starting point. Upon the return of wheel 21%) to normalthe springs 272 and 273 are unlocked and allowed to separate, therebystopping the mo tor 250, deenergizing relay 208, and extinguishing thelamp L. Upon deenergizing, relay 208 breaks the locking circuit of relay209 at armature 215, and at armature 217 disconnects ground G from thelocking circuit of relays 133 and 131. ielay 210 which is included inthis locking circuit is slow acting and hence does not retract itsarmature 211 until relays 233 and 2341 have had time to deenergize or atleast until relay 233 has opened the circuit at another point byretracting its armature 15st. Belay 183, by retracting its armature 157,also removes ground from conductor 171 and, therefore from commonconductor 171, with the result that the busy condition is removed fromother relay equipments in the group associated with sender N.Furthermore, at armature 155 the circuit of relay 203 is broken, whichrelay now deenergizes to again connect common conductor 171 with commonconductor 201, such being the normal condition.

Relay 13 1, which was deenergized simultaneously with relay 133, has nowreconnected the trunk conductors 161 and 163 with the right handwindings of the repeating coil R", these windings being conductivelyconnected by way of the upper winding of the electro polarized relay126, Now when the called subscriber answers his telephone the directionof current flow in the trunk conductors 161 and 163 is reversedaccordingly to the well known practice by a so called reversing relay inthe its upper armature 135, and at armature 136 short-circuits the lowerand high resistance winding of relay 128. As a result of this latteroperation suificient current is permitted to fiow over the inter-oflicetrunk comingfrom the'No. 1 oiiice to energize relay 6 of cord circuit C,whereuponthis relay is operated to extinguish the supervisory lamp Lthis notifying the A operator that the call has been answered.

The desired connection has now been es- So much of the talking circuitas is shown is in heavy lines, and being of the usualcharactergtheentire circuit will be understood without difi'iculty;

When the subscribers have finished talking they. will replace theirreceivers as is customary. Upon the replacement of the receiver atsubstation Athe supervisory lamp L is lighted as previously explained.When i the receiver is replaced at the called stationwhose lmetermmates1n the N0. 3 or automatic oiiice the direction of current fiow in trunkconductorsltiland 163 will the circuit of supervisory lamp L By thedisconnect signals thus exhibited the A operator is notified that theconversationis over with. and she will accordingly pull down theconnection. By the removel of the plug from jack J the primary switch Pis restored to normal,- and in addition the energizing circuit of relay128 is broken.

Relay 128,upon deenergizing, breaksthe circuit of relay 129, whosedeenergization is followed by the deenergization of relays 130, 131, and127 and by the extinguishing of lamp and restoration of the signal V.Relay 130 breaks the holding cir cuit of relay 106 of the secondaryswitch C which also restores; and relay 129 opens the bridge acrosstrunk conductors 161 and 163 thereb causing the release of the auto- 7 Qmatic switches,,whereupon all the apparabus in use wlll have beenrestored to normal. An explanationwill' now be made of certain otherfeatures whichwere not covered before because it was not thoughtadvisable to digress from the description of the routine operations. InFig. 5 are shown three relays 111, 112, and 113,.which are common to thethree groups or trunks associated with tablished and conversation mayproceed.

senders N, N and N respectively; and a fourth relay 114, which is commonto all the groups of relay equipments at all the positions which areaccessible to the secondary switches. Relay 111 may be energized in twoways; either by the closing of a circuit which includes armature 1 11 ofrelay 129 of the first relay equipment M in the group, the armaturelat-1 which is similiarly located in the second relay equipment of thegroup, and corresponding armatures in all the other relay equipments ofthe group; or by grounding conductor 168-at relay 202 or 203. It will beseen then that relay 111 will be energized when all the trunks or relayequipments 111' the group controlled by sender N are busy, and that itwill also be energized whenever the sender itself is busy, whether therelay equipments are all busy or not. Relay 112, associated with thegroup of relay equipments controlled by sender N is energized in asimiliar manner, a little more of the circuit being shown becauserelayequipment M is the second in the group rather than the first. Relay 113(circuits not shown) is energized responsive to busy conditions in thethird group in the same manner. There is a similar relay associated witheach of the other groups of relay; equipments to which the secondaryswitches haveaccess, and in the present embodiment of the inventioncomprising six operators senders (see Fig. 2) there will be three morerelays arranged like the ones shown, the circuit through these omittedrelays being indicated by the dotted conductor. It will be seen now thatwhen none of the groups of relay equipments are in; condition to receivea call, each group being busy either by reason of the fact that all therelay equipments themselves are busy or because the as sociated senderis in use, then all the relays 111, 112, etc.,will be energized and acircuit will be established for relay 11 1. Relay 11 1,

upon energizing, disconnects ground from the common conductor 109. If weassume now that a secondary switch, the switch S for example, isseized-in the process of extending a connection from the No. 1 ofiice,

when relay 107 is energized over the trunk conductors it will be unableto close the en ergizing circuit of relay 108, the secondary switchbeing thereby prevented from rotating in search of an idle trunk. Thisis done because rotation would be useless, there being in fact no trunksidle at th s tune.

i/Vhile the call is being held up in this 3 will rarely occur that thecondition will endure for long; and as soon as some group of relayequipn'ients at the No. 3 exchange becomes accessible ground will berestored to conductor 109 and the switch S will operate as usual.

It has been described how the test contacts of the relay equipments ineach position are normally tied together by means of the commonconductors 171 etc., and the common conductor 201. This arrangement isdesigned to and ordinarily does render the entire position busy whilethe operator is engaged in'setting up a call and any sender busy whileit is transmitting impulses thereafter, tho the position may then beaccessible via trunks associated with other senders.

Nevertheless, it-does happen at comparatively rare intervals that twocalls will come in at the same time at the same position, generallybeing due to two secondary switches being seized at exactly the sameinstant, or it maybe due to detective busy test circuits. Although asstated this trouble occurs so seldom that it could perhaps be neglected,yet under certain conditions it may be considered worth while to preventits ill effects and I have devised means-for doing so. Suppose thatcalls come in to the relay equipments M and M simultaneously. Certainrelays pull upin both relay equipmentsuntil finally relays 132 and areenergized, followed by the energization of relays 202 and 302. llelay202 disconnects ground from conductor 2&1 and hence from conductor 364which is included in: the energizing circuit of relay 332. It followsthat although relays 132 and 382 both operate at once or rather start tooperate, the latter relay will immediately fall bacl; so that only onecall will be extended to the operator which is the call received atrelay equipment ill, the other call being heldup temporarily while theoperator is setting the sender N. As soon as sender l is'startedtransmitting impulses relay 202 oe aergizes thereby permitting relay tooperate and extend the delayed call to the operator; meanwhile and untilthis occurs the A op erator is given a busy signal from the busyignalling machine Q3 It will be seen that :he normally groundedconductor 24:1. is coped through contacts of relays 202 and 30:,associated with senders N and N respectively, so that the sender ll willhave l'erence over the othersenders whenever ...unultaneous calls arereceived at the position, and sender N will have preference over senderN under similar circumstances. This takes care of calls receivedsimultaneously at relay equipments associated with diilerent senders.But suppose two callsare received simultaneously at relay equipmentscontrolled by the same sender. To take care of this situation each ofthe conductors such as conductor is looped through normally closedcontacts or" the several relays, such as relay 33a, of the several relayequipments or the group. Fig. 6 shows this very clearly, conductor 86%being looped through normally closed contacts of a relay in the 1strelay equipment which corresponds to relay 83d, thence through normallyclosed con tacts oi relay relay equipment M thence through normallyclosed contacts of a relay in the third relay equipment whichcorresponds to relay 83d, and thence through normally closed contacts(notshown) of similar rela s in all the other relay equipments inthe'group, there being a branch ta en off at each relay equipment forthe purpose or operating the relays such as relays 332. Thus it willbeseen that in the case of calls receivedsimultaneously atrelayequipments of the same group, the call received at the relayequipment which is closest to the grounded end of conductor 364: (orsimilar conductor) will have the preference.

Another feature relates-to the provision of means whereby an operatorcan restore a sender to normal and reset itin case she .mahes a mistakein registering a number.

Suppose the operator is setting up a number on sender It andaccidentally depresses a wrong digitlzey. To go ahead under thesecircumstances and operate the starting hey would result in giving thecalling party the wrong number. Instead therefore she will actuatemomentarily the release .rey (Fig. 0) thereby closing circuits forrelays 205 and 209. Upon energizing, relay 205 locks itself to ground Gand also closes a circuit for relay 20% which relay grounds conductors16 i and 165 in order to maintain the relay equipment, M- for example,in the status-quo, so to speak, while the sender is running down orreturning to normal. This operation is initiated by the energization oirelay 209, as has previously been described, and the automatic switchesare prevented from operating by the opening of the impulse transmittingcircuit at armature 223 or" relay 205. Vhen thesender has returned tonormal relay 205 will be unlocked (this will e clear it the function oislow acting relay 210 is recalled) and relay 204; will decnergisie aninstant later, restoring the circuits over conductors 164 and 165 totheir former condition. The operator is able to tell when the sensor hascompletely restored by the extinguishing of lamp T 6 and M she will thenreset the sender correctly.

What I claim as my invention is:

1. In a telephone system, two manual ollices an automatic o'hice,inter-oiiice trunk lines connecting said offices, A operators at eachmanual ol'lice for receiving and extending inter-ofiice calls to theproper ofice, B opera- 2. In a telephone system, two ofiicesor exchangesprovided wi'th'manual connecting apparatus, for connecting subscriberslines, third ofiice provided with automatic switches for connectingsubscribers lines,

intero1'fice trunk lines connecting said of fices,A operatorsat eachmanual office for receiving and extending inter-office calls to theproper oiiice, B operators at all of said offices for completing int-erofiice calls, such calls being completed at the said third oflice bymeans of automatic switches, other automatic switches at the manualofices, and suitable connectingapparatus and circuits thereforassociated with said inter-office trunk lines whereby the A operators inex tending inter-ofiice calls control said last mentioned switches toselect trunk lines to the proper 'oflices and perform the same routineoperations whether calls are being extended to the other manual officeor to the saidautomatic ofiice.

8. In a-telephone system, an Aboard divided into sections, eachcomp-rising a I plurality" of positions, a separate outgoing trunkmultiple for each section, a separate group of trunking switches'foreach mul 'tiple, and a plurality of inter-oflice trunk lines accessibleto all of said switches in common. V

4. ln a telephone system, an A board divided into sections, eachcomprising a plurality of positions, groups of automatic trunkingswitches, a separate outgoing trunk multiple extending from eachsectionand terminating in a plurality ofsaid groups of switches, groupsof inter-oflice trunk lines accessible, respectively, to the said groupof switches in which one of said multiples terminates, and multipleconnections-whereby the groups of switches forming terminals ofsaidothermultiples are given access to said groups of trunk lines also.

p 5. In a telephone system, two switch board sections each comprising aplurality of A operators positions, a group of trunklines multipledthroughout the first section and divided into sub-groups, each sub-grouphaying an associated group of primary switches in which the trunk linesthereof terminate, another groupof trunk lines multipled throughout theother of said sections, audalso divided into sub-groups,the trunk linesof each sub-group also terminatingin an associated group of primaryswitches, a

plurality of groups of inter-office trunk lines, there beinga group ofsaid inter-office trunk lines accessible to the primary switches of eachsub-group multipled'in the first section, and multiple branches of saidgroups of inter-oflice trunk lines accessible to said groups of primaryswitchesof the sub-groups multipled in the second section. 7 6. In atelephone system, a plurality of trunk lines connected to multiple jacksin a plurality of A "operators positions, a group of automatic trunkingswitches in which said trunk lines terminate, a second plurality oftrunk lines connected to multiple jacks in a different plurality of Aoperators positions, a second group of automatic trunking switches inwhich said sec{ ond group of trunk lines terminate, a third plurality oftrunk lines accessible to switches in both of said groups andterminating in a third group of autotrunking switches, a plurality of Boperators positions and a plurality of cord circuits at each position,and suitable connections whereby each i switch in said third group isgiven access to cord circuits in all of said B positions.

7. In a telephone system, two switch boardsections each comprising aplurality of A operators positions, agroup of trunk lines multipledthroughout the first section and divided into sub-groups, each sub-grouphaving an associated group of primary switches in which the trunk linesthereof terminate, another group of trunk lines multipled throughout theother of said sections, and also divided into sub-groups, the trunklines of each sub-group also terminat-. ing in an associated group ofprimary switches, a plurality of groups of inter oilicetrunk lines,there being a group of said inter-otfice trunk lines accessible to theprimary switches of each sub-group multip ied in the first section,multiple branches of said groups of inter-oiiice trunk lines accessibleto said groups of primary switches of the sub-groups multipled in thesecond section, a plurality'of B-operators cord circuits, and aplurality of secondary switches for ex tending said inter-oflicetrunklines into connectionwith said cord circuits.

8.111 a telephone system, two switch lines of each sub-group alsoterminating in an associated group of primary switches, a plurality ofgroups of 1nter-oilice trunk lines, there bemg a group of saidinter-oiiice

